Machine and method for forming helically wound paper tubes having improved mechanical resistance

ABSTRACT

The invention relates to a machine for producing a tubular product (T) by means of helical winding of strips of web material, comprising a mandrel ( 4 ) and a winding member ( 7 ) to helically wind the strips (S 1,  S 2 ) of web material around said mandrel. To improve adhesion between the strips at least one pressure member ( 31 ) is provided, cooperating with the mandrel, disposed downstream or upstream of the winding member ( 7 ) with respect to the direction of advance (fT) of the tubular product being formed on said mandrel. The pressure exerted by the pressure member promotes adhesion of the strips forming the product.

TECHNICAL FIELD

The present invention relates to a corewinder, that is, a machine ordevice used to produce tubular products from strips of web materialwound helically about a mandrel and glued to form the finished product.

The invention also relates to a method for producing tubular products ofthe aforesaid type.

STATE OF THE ART

In the production of rolls of web material, for example rolls of toiletpaper, rolls of kitchen towels, rolls of non-woven fabric, rolls ofadhesive tape, plastic film, metalized film or the like, tubes ofcardboard or another material are commonly utilized as winding cores,obtained by overlapping and staggered winding of at least two strips ofweb material bonded together. Winding is performed by machines calledcorewinders, which have a forming mandrel (fixed or supported idle aboutits axis) about which strips of web material previously provided with alayer of glue are wound. Usually, winding is obtained by means of awinding member, typically a continuous belt, which forms a helical turnabout the mandrel and causes the strips of web material to be drawn andwound. The winding member provides thrust to the helically wound strips,to form the tubular product and make it advance along the windingmandrel.

Examples of machines of this type are described in the U.S. Pat. Nos.3,150,575; 3,220,320; 3,636,827; 3,942,418; 5,468,207; 5,873,806.

The strips of web material are wound continuously and form a continuoustube, which is then cut into sections of the required length by means ofcutting members disposed along the tube being formed.

The continuous belt utilized to obtain winding of the turns of webmaterial is of a lesser width than the width of the strips of saidmaterial. The purpose of this is to prevent the glue, extruding alongthe edges of the turns by pressure exerted by the belt, from soilingsaid belt. This means that in the area in which it is required most, thepressure exerted is insufficient to obtain reciprocal adhesion of theoverlapping turns of the two or more strips forming the tube.

One of the problems encountered in the production and subsequent use ofthese tubes consists in the fact that the quality of gluing between thehelical strips of web material is not always sufficient to maintain theintegrity of the tube. In fact, the tubular product may break whiletraveling along the forming mandrel if gluing is not sufficient tostabilize the turns being formed on said mandrel. Another critical pointin the formation of tubular products is encountered in the area in whichthe continuous tubular product is cut into sections. Also in this areathere may be problems of adhesion of the glue with consequentdeterioration or localized breakage of the product.

Even when the product comes out of the corewinder in integralconditions, imperfect gluing of the strips forming it may give rise tofurther drawbacks during use of the tubes as winding cores for rolls.

In fact, in many applications, for example in the production of rolls oftoilet paper or kitchen towels, the rolls that are wound on the tubularcores must subsequently be cut crosswise to their axes into small rollsof an axial length equal to the axial dimensions of the finishedproduct. In the saw machines that are utilized for this purposedrawbacks occur frequently due to the fact that the knife making thecut, interfering with the strips of web material forming the tubularwinding core, cause partial breakage thereof. Breakage takes place atthe level of the cutting plane, where the blade intersects the edge ofthe innermost strip of web material. The stress applied by the blade,due to friction, causes partial detachment of the strip of web materialfrom the tubular inner wall of the winding core. This breakage isunacceptable to the manufacturers of rolls, as it has a negative effecton the appearance of the finished product. To a certain extent, it mayalso constitute a functional drawback in the finished product, as itimpedes insertion onto the dispensing device.

Other problems that can occur in the production of tubes are recognizedin the fact that the poor quality of adhesion between overlapping stripsmakes it necessary to operate the corewinder at a lower speed withrespect to its maximum design speed, with consequent decrease inproductivity, that tubes cannot withstand the high speeds reachable bythe rewinding machine employing them, and that tubes may be damagedduring storage, that is while being stored between the corewinder andthe rewinding machine utilizing them.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to produce a corewinder thatovercomes the drawbacks mentioned above making it possible to obtain atubular product, which has greater resistance and in particular improvedreciprocal adhesion of the helical strips of which it is formed,allowing high production speeds and greater efficiency in the productioncycle to be reached.

According to a further aspect, the object of the present invention is toproduce a method making it possible to obtain with a corewinder a moreresistant tubular product, in particular characterized by improvedreciprocal adhesion of the helical strips of web material forming thetubular product.

These and other objects and advantages, which shall be apparent to thoseskilled in the art by reading the text hereunder, are obtainedessentially with a corewinder, that is, a machine for producing atubular product by helically winding strips of web material, comprisinga mandrel and a winding member to helically wind strips of web materialabout said mandrel, provided with at least one pressure membercooperating with said mandrel, associated with the mandrel and disposedalong the path of advance of the tubular product being formed on saidmandrel, the pressure exerted by said pressure member promoting adhesionof the strips forming the product. The pressure member may be positionedeither downstream of the winding member or winder, or upstream of it,where the turns of web material are formed. When the pressure member ispositioned upstream of the winder problems of friction of the strips ofweb material on the mandrel are reduced.

According to an advantageous embodiment of the invention, the pressuremember may comprise a wheel and an actuator to push the wheel and themandrel against each other. Alternatively, two wheels may be alsoprovided, acting in different areas of the tubular product being formed,for example and advantageously at the level of the helical line formedby the adjacent edges of the outermost strip and of the innermost strip,respectively, forming the tubular product. In this way adhesion of theturns along the outer surface and also along the inner surface of theproduct is improved, with advantages during production of the rolls thatare wound on the sections of the tube formed and subsequently cut intosmall rolls with a lesser axial length.

When the pressure member has one or more wheels, the circular edge ofsaid wheel or of each or said wheels is advantageously and preferablydisposed with an inclination, with respect to the axis of the mandrel,essentially equal to the inclination of the helical winding of saidstrips of web material.

To increase the localized pressure applied by the wheel, this may beequipped with projections or protuberances. For example, annularprojections or protuberances may be provided, although preferablyprotuberances in the form of teeth, analogous to the teeth of a gear,will be provided.

When the pressure member has two wheels, these may be disposedadvantageously so as to reduce or eliminate the need to provideauxiliary supports for the mandrel, that is, so that one wheel providesthe reaction force required to support the mandrel against the stressapplied to the other wheel. For example, the two wheels may bepositioned staggered by around 180° about the axis of the mandrel and ina position whereby the straight edge that unites their contact pointswith the tubular product being formed on the mandrel is more or lessorthogonal to the axis of the mandrel and intersects it.

Further advantageous characteristics and embodiments of the machineaccording to the invention are indicated in the accompanying dependentclaims and shall be described with reference to the examples ofembodiment.

According to a different aspect, the invention also relates to a methodfor producing a tubular product wherein at least a first strip and asecond strip of web material, staggered with respect to each other, arehelically wound about a winding mandrel by means of a winding member,the two strips being glued to each other. Characteristically, accordingto the invention, pressure is applied to the outer surface of thetubular product being formed about said mandrel, downstream of saidwinding member to stabilize adhesion between said two strips. Thispressure is advantageously applied for example around the joining linebetween adjacent turns of the first strip of web material, forming theoutermost layer of the tubular product. Alternatively, or incombination, said pressure may be applied to the outer surface of thetubular product at the level of the joining line between adjacent turnsof the second strip of web material, forming an inner layer of thetubular product.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be better understood with reference to thedescription hereunder and to the accompanying drawings, showing anon-limiting practical embodiment of the invention. In the drawing,where equivalent or corresponding parts are indicated with the samereference numerals:

FIG. 1 shows a side view of a machine according to the invention;

FIG. 2 shows a local section according to II-II in FIG. 1;

FIG. 3 shows a local section according to III-III in FIG. 2;

FIG. 3A shows a local section according to IIIA-IIIA in FIG. 2;

FIG. 4 shows a side view of the wheel of the machine in FIGS. 1 to 3;

FIG. 5 shows a side view according to V-V in FIG. 4;

FIG. 6 shows a local section analogous to the section in FIG. 2, in amodified embodiment of the invention;

FIG. 7 shows a section according to VII-VII in FIG. 6; and

FIG. 8 shows a side view of the wheels and of the tube being formed inthe arrangement in FIGS. 6 and 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows as a whole a corewinder to which the present invention isapplied. The machine shown has a structure corresponding essentially tothe one described in the U.S. Pat. No. 5,873,806, which should bereferred to for a detailed description of the components of the machine,not of interest in the description of the present invention. Inparticular, the cutting members of the continuous tube, which may beproduced as in the aforesaid US patent or in any other suitable way, arenot shown.

It must also be understood that the invention may also be applied tomachines with a different structure, as long as they are provided with aforming mandrel to form the tubes, which may either be fixed or rotatingabout its axis.

Briefly, and limited to the parts of interest in the presentdescription, the machine in FIG. 1, indicated as a whole by 1, comprisesa load-bearing structure 3 from which a mandrel 4 is supported in acantilever fashion, a first end thereof being constrained to theload-bearing structure 3 by means of a sleeve 8. The opposed end of themandrel 4 terminates in proximity to the cutting area or to a conveyorbelt 10 onto which the individual tubular products obtained by cutting atube T, formed continuously as described hereunder about the mandrel 4,are unloaded. The cutting system that divides the tube into sections isnot shown and is per se known.

To form the tube T, two continuous strips of cardboard or of anothercontinuous web material indicated with S1 and S2, are fed to thecorewinder 1. These are wound helically about the mandrel 4 with the aidof a continuous belt 7, which has two branches 7A and 7B, driven abouttwo pulleys 9 and 17, of which 9A and 17A indicate the respective axesof rotation. The branch 7A forms a helical turn about the mandrel 4 andabout the strips of web material S1 and S2 being wound. The numeral 19indicates the motor which draws the driving pulley 17 in rotation,causing movement of the belt 7.

Inclination of the assembly formed of the pulleys 9, 17, of the belt 7and of the motor 19 is adjustable by means of a threaded bar 21 and ahandwheel 23, so as to adjust inclination of the helical turns formed bythe two strips S1, S2 about the axis of the mandrel 4.

The two strips S1 and S2 are wound overlapping and staggered, so that ahelix formed by the turns of the outermost strip S1 overlaps a helixformed by the turns of the innermost strip S2. The two turns arestaggered so that the joining lines between adjacent turns of theinnermost helix are covered by the turns of the outermost strip. The twostrips may, for example, be staggered by half a pitch.

A glue is applied to the inner surface of the outer strip S1 and/or tothe outer surface of the inner strip S2 in a way per se known and notshown, to make the two turns adhere to each other. As mentionedhereinbefore, the width of the belt 7 is lesser than the width of thestrips S1, S2 to prevent the glue from soiling it.

Along the extension of the mandrel 4, disposed downstream of the windingmember of the strips S1, S2, formed by the belt 7, is a pressure memberindicated as a whole with 31, comprising a toothed or knurled wheel 33,shown in detail in FIGS. 4 and 5. As can be seen in these figures, thecircular perimeter of the wheel 33 is provided with teeth orprotuberances 34 parallel to the axis of rotation of the wheel. It mustbe understood that the arrangement of the teeth 34 may differ from theone shown. For example, the teeth 34 may be inclined analogously to theteeth of a helical gear. Yet again, they may not be continuous, butrather discontinuous, or may have a concave frontal surface. Generally,the teeth may have a concave profile, so as to produce a larger contactarea with the tube T being formed, even to have contact on more or lessthe entire extension of the tooth. In this way the helical band in whichthe wheel exerts its action on the tube T is increased.

The wheel 33 is supported with its axis B inclined with respect to theaxis A of the mandrel 4. The degree of inclination is such that it rollson the tube T being formed about the mandrel along a line that hasessentially the same inclination as the turns formed by the strips S1and S2. Inclination of the axis of the wheel 33 is adjustable, as isinclination of the turns formed by the strips S1 and S2. The position ofthe wheel 33 with respect to the area of formation of the turns ofstrips S1, S2 forming the tube is adjusted so that the wheel is incontact with the outer surface of the tube at the level of the lineseparating two adjacent turns formed by the outermost strip S1. In thisway the wheel 33 exerts pressure along a helical band overlapping thehelical line defined by the juxtaposed edges of adjacent turns of thestrip S1.

The pressure exerted by the wheel may have a dual effect of stabilizingthe turns forming the tube T. On the one hand, the pressure increasesthe adhesion implemented by the glue applied between the two strips. Onthe other, high pressure may also provide an additional effect ofply-bonding between the overlapping strips S1 and S2.

The pressure with which the wheel 33 acts against the outer surface ofthe tube T being formed is provided by a piston-cylinder actuator 35,the stem 37 of which is constrained to a supporting rod 39 (FIG. 2)integral with a supporting member 41 of the wheel 33. The supporting rod39 slides freely in a sleeve 43 and is torsionally constrained to thelatter. For this purpose the rod 39 may have a non-circularcross-section and the sleeve 43 may have a through hole corresponding inshape. Or, as in the example shown, the supporting rod 39 may have aslotted through hole, elongated according to the direction of the axisof said rod, inside which a transverse pin, integral with the sleeve 43,engages.

The sleeve 43 has a flange 45 equipped with slotted holes 47 (see inparticular FIG. 3), by means of which said sleeve may be fixed, in anangularly adjustable position, to a supporting structure 49, integralwith the structure 3. A bracket 51, to which the body of thepiston-cylinder actuator 35 is constrained, is also fixed rigidly to thesupport 49.

The actuator 35 can press the wheel 33 against the mandrel 4 even with arelatively high force. To provide sufficient reaction and supportingforce to the mandrel, under the wheel 33, in this embodiment, two restsare provided, composed of two rollers 53 carried idle by supports 55integral with pins 57 fixed to the structure 49. The pins are angularlyadjustable so that the rollers 53, just as the wheel 33, can be inclinedso as to roll on the cylindrical surface of the tube T being formedalong a helical line with the same inclination as the strips S1, S2forming said tube. In this way rubbing between the rollers and the tubeT is prevented. As can be seen in particular in FIG. 1, the rollers 53and the wheel 33 are disposed in the space so that the contact points ofthese members with the tube T being formed about the mandrel 4 lie on aplane essentially orthogonal to the axis A of the mandrel 4, to preventmoment stresses on said mandrel.

With the layout described hereinbefore, the corewinder operates asfollows. The strips S1, S2 are fed continuously and wound about themandrel 4, which may be a fixed mandrel or mounted idle to rotate aboutits axis. Alternatively and in a known way the mandrel may be in partfixed and in part idle. The staggered turns formed by the two strips S1,S2 are pressed against each other by the belt 7 to stabilize reciprocalgluing of the strips wound in a spiral and form the continuous tube T.This advances according to the arrow fT rotating about itself towardsthe cutting means disposed along the path of the tube and not shown, tobe cut into sections of the required length. When the tube T passesthrough the pressure member 31, the wheel 33 applies high pressure bymeans of the protuberances 33 thereof along the edge area of the outerturns formed by the strip S1, to obtain better stability and resistanceof the tubular product. The pressure improves bonding of the stripsthrough the effect of the glue, and, if necessary, with adequatepressure values add characteristics of the cardboard or other materialforming the strips S1, S2, ply-bonding may be obtained.

To obtain improved bonding of the strips forming the tube T also at thelevel of the helical line defined by the juxtaposed edges of the innerturns, formed by the strip S2, in an improved embodiment of thecorewinder according to the invention, shown in FIGS. 6 to 8, isprovided with a pressure member equipped with two wheels rather than asingle wheel.

In fact, in this case the pressure member, once again indicated with 31,comprises two wheels 33A, 33B, each of which may be produced like thewheel 33 shown in FIGS. 4 and 5. The two wheels 33A, 33B, of which B1and B2 indicate the respective axes of rotation, are carried by supports41A, 41B and rods 39A, 39B, guided in sleeves 43A, 43B equipped withflanges 45A, 45B. The numerals 35A, 35B and 37A, 37B indicate thepiston-cylinder actuators and relative rods, constrained to the brackets51 of the load-bearing structure 49, which press the two wheels againstthe mandrel 4 and the tube T being formed about it.

The two wheels are superimposed so that the stresses applied to themandrel are cancelled out. This makes it unnecessary to provide furthersupports for the mandrel. However, the wheels may also be disposeddifferently and combined with supports analogous to the rollers 53 ofthe previous embodiment or other equivalent supports.

As can be observed in the schematic representation in FIG. 8, the wheel33A is disposed so as to act with its projections or protuberances 34 ina helical band along the joining line L1 defined by adjacent edges ofconsecutive turns formed by the outer strip S1. Therefore, it performsthe same function as the wheel 33 of the example shown in FIGS. 1 to 3A.The wheel 33B is positioned and inclined so that it acts on the outersurface of the strip S1 at the level of the line L2 defined by thejuxtaposed edges of two adjacent turns formed by the inner strip S2.

This layout thus allows high pressure to be applied along the helicaledge lines of the strips S1, S2, both on the outer surface and on theinner surface of the tube T, improving the quality of the product. Thisadvantage is essentially obtained without any increase in construction,as the additional wheel means that the reaction supports formed by therollers 53 are no longer required. A single actuator 35A may even beprovided, eliminating the actuator 35B and providing a simple, angularlyadjustable support for the lower wheel 33B (or, vice versa, for theupper wheel).

However, the advantage of increased resistance in the finished productmay also be obtained by placing the wheels 33A, 33B in angularlydifferent positions to the one shown with respect to the axis A of themandrel 4. In this case, auxiliary supports analogous to the rollers 53may be provided.

In both the examples illustrated the wheel(s) 33; 33A, 33B may bemotorized, to provide a thrust on the tube that facilitates its advancealong the mandrel 4.

In the examples shown the wheel(s) constituting part of the pressuremember is/are disposed downstream of the winding member, that is, of thebelt 7. Nonetheless, the wheel(s) may also be disposed upstream of thebelt, in the area in which the turns formed by the strips S1 and S2start to form.

Moreover, the pressure member may be constrained to the support on whichthe motor 19, the pulleys 9 and 17 and the belt 7 are disposed, ratherthan directly to the fixed structure 3 of the machine.

When the tubular product is formed with partial overlapping of the turnsformed by the strips of web material, the wheel(s) may in any case bedisposed at the level of one edge of the respective strip.

It is understood that the drawing merely shows a practical embodiment ofthe invention, which may vary in forms and layouts without howeverdeparting from the scope of the concept on which the invention is based.Any reference numerals in the appended claims are provided purely tofacilitate reading in the light of the description hereinbefore and ofthe accompanying drawings, and do not limit the scope of protectionwhatsoever.

1. A machine for producing a tubular product (T) by means of helicalwinding of strips of web material, comprising a mandrel (4) and awinding member (7) to helically wind the strips (S1, S2) of web materialaround said mandrel, characterized by at least one pressure member (31)cooperating with said mandrel, disposed along the path of the tubularproduct being formed on said mandrel, the pressure exerted by saidpressure member promoting adhesion of the strips forming the product. 2.Machine as claimed in claim 1, characterized in that said pressuremember comprises at least a wheel (33; 33A; 33B) and an actuator (35;35A; 35B) to stress the wheel and the mandrel against each other. 3.Machine as claimed in claim 2, characterized in that said wheel ispositioned to act on the outer surface of the tubular product, at thelevel of the edge line (L1) of adjacent turns of the outermost strip(S1) of web material forming the tubular product (T).
 4. Machine asclaimed in claim 3, characterized in that said the circular edge of saidwheel is disposed with an inclination, with respect to the axis (A) ofthe mandrel, essentially equal to the inclination of the helical windingof said strips (S1, S2) of web material.
 5. Machine as claimed in one ormore of claims 2 to 4, characterized in that the circular edge of saidwheel has a series of protuberances (34).
 6. Machine as claimed in claim5, characterized in that said protuberances have the form of a toothing.7. Machine as claimed in one or more of claims 2 to 6, characterized inthat the inclination of the axis of rotation (B) of the wheel (33; 33A;33B) with respect to the axis (A) of the mandrel (4) is adjustable. 8.Machine as claimed in one or more of claims 2 to 7, characterized inthat said wheel (33; 33A; 33B) is carried by a support (39, 41; 39A,41A; 39B, 41B) sliding in a sleeve (43; 43A; 43B), and torsionallyconstrained to said sleeve.
 9. Machine as claimed in claims 7 and 8,characterized in that said sleeve can be locked in an angularlyadjustable position with respect to a fixed load-bearing structure (49).10. Machine as claimed in claim 9, characterized in that said sleeve(43; 43A, 43B) comprises a flange (45; 45A, 45B) with slotted holes (47)to lock said sleeve in an angularly adjustable position.
 11. Machine asclaimed in one or more of the previous claims, characterized in thatsaid pressure member (31) comprises at least a supporting element (53)for said mandrel (4).
 12. Machine as claimed in claims 2 and 11,characterized in that the pressure member comprises two angularlystaggered supports (53) that provide the mandrel with a reaction forceto the stress applied by said wheel (33).
 13. Machine as claimed inclaim 12, characterized in that the contact points between said wheeland the product being formed on the mandrel and between said at leastone support and said product lie approximately on a plane orthogonal tothe axis of the mandrel.
 14. Machine as claimed in one or more of theprevious claims, characterized in that said pressure member (31)comprises two wheels (33A, 33B) acting on the tubular product (T) beingformed around said mandrel (4).
 15. Machine as claimed in claim 14,characterized in that said two wheels are positioned to act on the outersurface of the tubular product, one at the level of the joining line(L1) of adjacent turns formed by the outermost strip (S1) of webmaterial, and the other at the level of the joining line (L2) ofadjacent turns formed by the innermost strip (S2) of web material. 16.Machine as claimed in claim 14 or 15, characterized in that said twowheels are disposed staggered by around 180° about the axis (A) of themandrel (4) and in a position wherein the straight line uniting theircontact points with the tubular product being formed on the mandrel isapproximately orthogonal to the axis of the mandrel.
 17. Machine asclaimed in one or more of the previous claims, characterized in thatsaid wheel(s) (33; 33A, 33B) is/are motorized.
 18. Machine as claimed inone or more of the previous claims, characterized in that said pressuremember is positioned downstream of the winding member.
 19. Machine asclaimed in one or more of claims 1 to 17, characterized in that saidpressure member is positioned upstream of the winding member.
 20. Amethod for producing a tubular product wherein at least a first strip(S1) and a second strip (S2) of web material staggered from each otherare wound around a winding mandrel (4) by means of a winding member (7),the two strips being glued to each other, characterized in that pressureis applied to the outer surface of the tubular product being formedaround said mandrel, along the path of the product being formed aroundsaid mandrel to stabilize adhesion between said two strips.
 21. Methodas claimed in claim 20, characterized in that said pressure is appliedaround the edge (L1) of a strip forming the adjacent turns that form theoutermost layer of said tubular product.
 22. Method as claimed in claim20 or 21, characterized in that said pressure is applied to the outersurface of the tubular product at the level of the edge (L2) of thestrip (S2) of web material, forming an inner layer of the tubularproduct.
 23. Method as claimed in one or more of claims 20 to 22,characterized in that said pressure is applied downstream of the windingmember.
 24. Method as claimed in one or more of claims 20 to 22,characterized in that said pressure is applied upstream of the windingmember.